Performance-based Impedance Control of a One Degree-of-Freedom Finger Extensor for Hand Rehabilitation

Encouraging post-stroke patients to perform self-initiated movements is an essential requirement to achieve motor learning during rehabilitation. Control schemes are hence designed around the central idea of modulating assistance/resistance provided during therapy based on the patient's performance. This ensures patients are challenged appropriately as per their capability. This paper describes the design and implementation of a novel performance-based impedance control algorithm on a one degree-of-freedom hand rehabilitation device. The control scheme modifies resistance provided to patients depending upon the force exerted by them at each instant of the therapy session. Prior to implementation of the control program, a system model describing the kinematics and dynamics of the device is developed. The control architecture and force flow between the controller and the device is described. Preliminary experiments have been performed on a healthy subject to evaluate the performance of the developed controller. Results reveal the efficiency of the controller in tailoring hand rehabilitation to each individual patient's level of impairment.